The effect of thiol-combining agents on polypeptide synthesis in cell-free system from Escherichia coli

Among the thiol-combining reagents studied 2,3-dicyano-1,4-dithiaanthraquinone, quajazulene, p-bromobenzylisothiocyanate, ethylester of 2-isothiocyano-3-methyl-butanoic acid, N-trichloromethylthiotetrahydrophthalimide and N,N-dimethyl-N′-phenyl-(N′-fluorodichloromethylthio) sulfamide exhibited a marked inhibitory effect on poly(U)-lysyl polyphenylalanine synthesis. These compounds inactivated the S-100 postribosomal supernatant fraction. A distinct inhibitory effect on ribosomes was found with two isothiocyanates, namely, ethylester of 2-isothiocyano-3-methylbutanoic acid and in particular p-bromobenzylisothiocyanate. The latter, however, did not influence the ribosomal peptidyl transferase activity measured in the presence of puromycin. All the compounds studied acted as inhibitors of the elongation factor EF-G. Particularly effective in this respect was 2,3-dicyano-1,4-dithiaanthraquinone. Several of the compounds investigated represent new thiol-combining reagents differing by their chemical reactivity with R-SH compounds as well as by other physico-chemical properties.